Molecular characterization of five serine protease genes cloned from Anopheles gambiae hemolymph

We identified five new serine protease cDNAs from the hemolymph of the mala ria vector, Anopheles gambiae. All five show sequence similarity to genes t hought to be involved in vertebrate or invertebrate defense responses. Sp14 A, Sp14D2 and Sp22D demonstrate changes in transcript abundance in response to bacteria injections. Sp14A and Sp14D2, as well as the previously charac terized Sp14D1, are induced by infection with the malaria parasite, Plasmod ium berghei. These three proteases, along with Sp18D, are related to a grou p of secreted proteases that have amino-terminal clip domains and trypsin-l ike substrate specificity. BLAST results and phylogenetic analyses group Sp 14A, Sp14D1 and Sp14D2 with the Drosophilia protease EASTER, and three prop henoloxidase activating enzymes from other insects. EASTER's substrate is S PAETZLE, a ligand involved in embryogenesis but also in activating anti-mic robial peptide synthesis. Their similarity to EASTER and immune inducibilit y suggest that one of these proteases may activate a SPAETZLE-like ligand d uring anti-parasite responses in mosquitoes. Alternatively, as potential pr ophenoloxidase activators, Sp14A, Sp14D1 or Sp14D2 may play a role in melan otic encapsulation of Plasmodium. (C) 2000 Elsevier Science Ltd. All rights reserved.